Research On Local Buckling Bearing Capacity Of High-strength Steel I-shaped Axial Compression Members

With the rapid development of China’s construction industry,more and more building structures are characterized by large span and many layers.As a building material,high-strength steel has become the preferred material for construction.The use of high-strength steel can not only reduce the dead weight of the structure,but also reduce the cross-sectional size of components and increase the use space of buildings.However,components made of such materials are extremely vulnerable to instability and damage.Therefore,it is very important to carry out stability research of high-strength steel.Through the combination of experimental research,simulation and theoretical research,the paper studies the local buckling bearing capacity of high-strength steel I-shaped members with different yield strengths of 460 MPa,550MPa,690 MPa,800MPa and 960 MPa,and proposes a design proposal method for the buckling bearing capacity of high-strength steel I-shaped members under axial compression.(1)The material mechanical properties of 800 MPa steel with a thickness of 7mm were measured by uniaxial tensile test and compared with the material mechanical properties of other strength steels.The results show ed that the yield ratio of high strength steels is mostly less than 0.8,and the elongation after fracture of most high strength steels is above 20%.In addition,the ultimate strain of steel decreases with the increase of yield strength of steel.The distribution pattern of longitudinal residual stress in the cross section of the specimen was measured by dividing method.Based on the local buckling tests of 12 welded I-shaped specimens with different slenderness ratios and width-to-thickness ratios,the local buckling stability of 800 MPa high strength steel axial compression members was studied.The results showed that the ultimate bearing capacity of the specimens decreases with the increase of slenderness ratio,increases with the increase of width-to-thickness ratio of flange and web,and the local buckling bearing capacity increases with the increase of width-to-thickness ratio of flange and web,but it is less affected by slenderness ratio.(2)The finite element software ANSYS was used to establish the model and the existing test results of high-strength welded I-shaped specimens with different yield strengths of 460 MPa,550MPa,690 MPa,800MPa and 960 MPa were compared with the simulation results.The results showed that the average error between the numerical analysis results and the test results of the ultima te bearing capacity of all specimens after local buckling was-1.38%,and the standard deviation was 4.98%;The average and standard deviation of errors in the numerical analysis results and test results of the local buckling bearing capacity were-0.2% and 4.28% respectively.Compared with the experimental results,the numerical simulation results ha d smaller errors,so the model was used for parametric analysis in the next chapter.(3)The finite element parametric analysis was carried out on the buckling performance of high strength steel I-shaped members with different yield strengths of 460 MPa,550MPa,690 MPa,800MPa and 960 MPa.The relationship between flange plate width-to-thickness ratio,web height-to-thickness ratio,member slenderness ratio,steel yield strength and initial defects of members was mainly studied.The results showed that the local buckling bearing capacity and the ultimate bearing capacity after buckling were closely related to the width-to-thickness ratio of the plate.The ultimate bearing capacity and local buckling bearing capacity of the member with width-to-thickness ratio exceeding the limit were not sensitive to slenderness ratio.The degree of influence of steel yield strength on local buckling bearing capacity decreased with the increase of width-to-thickness ratio.Initial geometric defects and residual stress had little effect on the ultimate bearing capacity of the component after local buckling,but have greater effect on the local buckling bearing capacity of the component.(4)Based on the test and finite element analysis results of the above five high-strength welded I-shaped specimens with different yield strengths,the calculation methods of the local buckling bearing capacity and the ultimate bearing capacity of high-strength steel axial compression members were proposed.The calculation results of the proposed formula are compared with the standard calculation values and test values at home and abroad.The results show that the proposed formula has better accuracy and safety.